Based on theory of electron beam optics,the beam optical calculations for animmersion lens and a unipotential lens have been performed.The computational results showthat the beam optical calculations are consistent to...Based on theory of electron beam optics,the beam optical calculations for animmersion lens and a unipotential lens have been performed.The computational results showthat the beam optical calculations are consistent to the ray tracing and that the beam emittanceis conserved,even if the third order aberrations exist.展开更多
The intensity dependence of the cesium D_(2)-line saturation absorption spectra in a nearly zero magnetic field was investigated theoretically and experimentally.By using rate equations the D_(2)-line saturation absor...The intensity dependence of the cesium D_(2)-line saturation absorption spectra in a nearly zero magnetic field was investigated theoretically and experimentally.By using rate equations the D_(2)-line saturation absorption spectra were calculated,which agree reasonably well with the experimental results.The variation of the spectra with different cell lengths was also reported and explained with theoretical calculation.展开更多
Surface self-diffusion anisotropy of tungsten on W(112)plane has been measured along(Ⅱ)and across(丄)channels existed on this plane by using the field emission fluctuation method in two forms of the probeholes.In the...Surface self-diffusion anisotropy of tungsten on W(112)plane has been measured along(Ⅱ)and across(丄)channels existed on this plane by using the field emission fluctuation method in two forms of the probeholes.In the round probehole the thermal activation energy E=13.0kcal,and the prefactor of the surface self-diffusion coefficient Dq=^.5X 70_7cm2s-1;in the long narrow rectangular slit,E(Ⅱ)=13.2kcal,D0(Ⅱ)=7.1×10-7crr^and E(丄)=6.2kcal,Do(丄)=1.8×10^(-9)cm^(2)s^(-1) at T=500-700K.The experimental data suggest that a W atom diffusing across channels should not climb over the channel wall,which would certainly require a much higher activation energy,but instead,displace an atom in the wall.This process reqwes a much smaller activation energy;however,since it involves concerted motion of at least two atoms,it will also have a much smaller prefactor.展开更多
Sub-natural linewidth optical-pumping dips have been observed in a homogeneously broadened. fluorescence line in Na atomic beam spectroscopy. To our knowledge, this is the first observation of sub-natural linewidth di...Sub-natural linewidth optical-pumping dips have been observed in a homogeneously broadened. fluorescence line in Na atomic beam spectroscopy. To our knowledge, this is the first observation of sub-natural linewidth dip by optical pumping. A theoretic explanation is given.展开更多
The microwave transition between two ground hyperfine sublevels of Cs atom has been observed by optidal pumping and optical detecting.The maximum population difference between"0-0"sublevels in single laser p...The microwave transition between two ground hyperfine sublevels of Cs atom has been observed by optidal pumping and optical detecting.The maximum population difference between"0-0"sublevels in single laser pumping case is achieved.The"Ramsey pattern"of"0-0"clock level transition and"Rabi"transition structures are obtained,and their main characters agree with the theoretical results.A better Cs beam atomic clock performance would be expected when the inject microwave frequency is locked into the center of the"0-0"clock level transition"in this experimental setup.展开更多
The polarization spectroscopy of Na D1 line with linearly polarized pumping light is studied theoretically using velocity-selective optical pumping model.The experimental results are in good agreement with the theoret...The polarization spectroscopy of Na D1 line with linearly polarized pumping light is studied theoretically using velocity-selective optical pumping model.The experimental results are in good agreement with the theoretical analysis.展开更多
The idea of free energy has been used in the discussion of physical conditions for nucleaton of clusters and or ultrafine particles on substrates.The physical picture of ultrafine particle growth are explained.,Condit...The idea of free energy has been used in the discussion of physical conditions for nucleaton of clusters and or ultrafine particles on substrates.The physical picture of ultrafine particle growth are explained.,Conditions of epitaxial growth are also discussed.展开更多
The abnormal saturation absorption signal of sodium atom D1 line has been observed in different experimental conditions.The explanation has been presented quantitatively using the velocity-selective optical pumping mo...The abnormal saturation absorption signal of sodium atom D1 line has been observed in different experimental conditions.The explanation has been presented quantitatively using the velocity-selective optical pumping model.展开更多
An optical field induced circular birefringence due to collision-induced Zee-man coherence in Sm with He has been observed.The integrated intensity and linewidth of the signal have been measured as a linear function o...An optical field induced circular birefringence due to collision-induced Zee-man coherence in Sm with He has been observed.The integrated intensity and linewidth of the signal have been measured as a linear function of buffer gas pressure.The cross section for destruction of orientation in the ground state of Sm with He has been obtained.展开更多
we present a few unique animal-like fractal patterns in ionized-clnster-beam deposited fullerene-tetracyanoquinodimethane thin films.The fractal patterns consisting of animal-like aggregates such as"fishes"a...we present a few unique animal-like fractal patterns in ionized-clnster-beam deposited fullerene-tetracyanoquinodimethane thin films.The fractal patterns consisting of animal-like aggregates such as"fishes"and"quasi-seahorses"have been characterized by transnission electron microscopy.The results indicate that the sall aggregates ofthe aninmal-like body are composed of many single crystals whose crystalline directions are generally different.The formation of tle fractal patterns can be attributed to the cluster-diffusion-lirnited aggregation.展开更多
A laser diode pumped cesium beam frequency standard had been built.The laser diode used for both optical pumping and detection is frequency-locked at the 4-4 transition of Cs D2 line.The Voltage controlled crystal osc...A laser diode pumped cesium beam frequency standard had been built.The laser diode used for both optical pumping and detection is frequency-locked at the 4-4 transition of Cs D2 line.The Voltage controlled crystal oscillator(VCCO)frequency is locked to the center of the Ramsey pattern of the microwave clock transition after frequency multiplying and synthesizing.The preliminary measurement of the frequency stabilities shows that the results are in agreement with the theory,and better results could be achieved by further improving the frequency stability of the laser diode.展开更多
A physical-mathematical model was proposed for the NMR relaxation processes,which can automatically identify the multi-relaxation process;the automatic separation of the spin-spin relaxation processes of water sample ...A physical-mathematical model was proposed for the NMR relaxation processes,which can automatically identify the multi-relaxation process;the automatic separation of the spin-spin relaxation processes of water sample in a home made phantom was carried out;two kinds of proton pure spin-spin relaxation time images and two kinds of proton computed pure density images have been obtained on a 1.0T supercondlrtive magnet MR-Scanner.展开更多
We report experimental studies on the photorefractive response of KNbO_(3) doubly doped with manganese and rubidium,iron and rubidium,respectively.Two-beam coupling response time in KNbO_(3):Mn:Rb is 3 to 10 times sho...We report experimental studies on the photorefractive response of KNbO_(3) doubly doped with manganese and rubidium,iron and rubidium,respectively.Two-beam coupling response time in KNbO_(3):Mn:Rb is 3 to 10 times shorter while the two-beam coupling gain coefficient remains almost the same when compare with that in KNbO_(3):Mn.On the other hand,under similar conditions,two-beam coupling response time in KNbO_(3):Fe:Rb is 6 times faster than that in KNbO_(3):Fe.展开更多
A probe-hole field emission microscope system,controlled by an Apple II computer,has been developed and operated successfully for measuring the work function of a single crystal plane.The work functions on the clean W...A probe-hole field emission microscope system,controlled by an Apple II computer,has been developed and operated successfully for measuring the work function of a single crystal plane.The work functions on the clean W(100)and W(111)planes are measured to be 4.67eV and 4.45eV,respectively.展开更多
The athermal bioeffects caused by nanosecond electromagnetic pulses with body cells was studied by using a broad band transverse EM-wave cell (BTEM CELL). The experimental system and preliminary mechanism analysis wer...The athermal bioeffects caused by nanosecond electromagnetic pulses with body cells was studied by using a broad band transverse EM-wave cell (BTEM CELL). The experimental system and preliminary mechanism analysis were presented.展开更多
Optical and microwave devices with nonlinear materials offer a series of novel phenomena and have many potential applications, so they have received more and more attention. There have been many papers which investiga...Optical and microwave devices with nonlinear materials offer a series of novel phenomena and have many potential applications, so they have received more and more attention. There have been many papers which investigated wave propagation in uniform optical waveguides with nonlinear materials and discovered that they possess the properties of self-focusing and bistability. However, there have rarely been reports on studying the 3-D nonlinear electromagnetic cavities. In the meantime among the methods used to analyze nonlinear optical waveguides, the most commonly used展开更多
A concept of frequency character of a chaotic synchronized system (CHSS) is proposed. The nature of the system can be described in the frequency domain with the concept. A simple model to measure the frequency charact...A concept of frequency character of a chaotic synchronized system (CHSS) is proposed. The nature of the system can be described in the frequency domain with the concept. A simple model to measure the frequency character is designed, and the characteristic curve of Chua’s CHSS is obtained. Some results from theoretical analysis and numerical simulation indicate that the system possesses multiband of frequencies with distinct features shown in each band. Thus it may offer various resources of frequencies, fn particular, it is capable of detecting weak signals drowned in noise in some bands. Both the concept of frequency character and the characteristic curve of CHSS provide a scientific basis for us to gain a deeper insight into the inherent function of information processing in CHSS, and to utilize properly the information resources of CHSS as well.展开更多
AI (Artificial Intelligent) control is just the up-to-date frontline of that kind of art, and the most merit it has is that it may provide us with an optimizing control, basing itself merely upon a rough understanding...AI (Artificial Intelligent) control is just the up-to-date frontline of that kind of art, and the most merit it has is that it may provide us with an optimizing control, basing itself merely upon a rough understanding of the plant to be controlled (e. g. an understanding of the type of its inertia, of the limits of variation of those parameters to be controlled, etc.), whenever its exact mathematical model is difficult, even impossible, to build up.展开更多
文摘Based on theory of electron beam optics,the beam optical calculations for animmersion lens and a unipotential lens have been performed.The computational results showthat the beam optical calculations are consistent to the ray tracing and that the beam emittanceis conserved,even if the third order aberrations exist.
基金Supported by the National Natural Science Foundation of China,。
文摘The intensity dependence of the cesium D_(2)-line saturation absorption spectra in a nearly zero magnetic field was investigated theoretically and experimentally.By using rate equations the D_(2)-line saturation absorption spectra were calculated,which agree reasonably well with the experimental results.The variation of the spectra with different cell lengths was also reported and explained with theoretical calculation.
文摘Surface self-diffusion anisotropy of tungsten on W(112)plane has been measured along(Ⅱ)and across(丄)channels existed on this plane by using the field emission fluctuation method in two forms of the probeholes.In the round probehole the thermal activation energy E=13.0kcal,and the prefactor of the surface self-diffusion coefficient Dq=^.5X 70_7cm2s-1;in the long narrow rectangular slit,E(Ⅱ)=13.2kcal,D0(Ⅱ)=7.1×10-7crr^and E(丄)=6.2kcal,Do(丄)=1.8×10^(-9)cm^(2)s^(-1) at T=500-700K.The experimental data suggest that a W atom diffusing across channels should not climb over the channel wall,which would certainly require a much higher activation energy,but instead,displace an atom in the wall.This process reqwes a much smaller activation energy;however,since it involves concerted motion of at least two atoms,it will also have a much smaller prefactor.
文摘Sub-natural linewidth optical-pumping dips have been observed in a homogeneously broadened. fluorescence line in Na atomic beam spectroscopy. To our knowledge, this is the first observation of sub-natural linewidth dip by optical pumping. A theoretic explanation is given.
文摘The microwave transition between two ground hyperfine sublevels of Cs atom has been observed by optidal pumping and optical detecting.The maximum population difference between"0-0"sublevels in single laser pumping case is achieved.The"Ramsey pattern"of"0-0"clock level transition and"Rabi"transition structures are obtained,and their main characters agree with the theoretical results.A better Cs beam atomic clock performance would be expected when the inject microwave frequency is locked into the center of the"0-0"clock level transition"in this experimental setup.
文摘The polarization spectroscopy of Na D1 line with linearly polarized pumping light is studied theoretically using velocity-selective optical pumping model.The experimental results are in good agreement with the theoretical analysis.
文摘The idea of free energy has been used in the discussion of physical conditions for nucleaton of clusters and or ultrafine particles on substrates.The physical picture of ultrafine particle growth are explained.,Conditions of epitaxial growth are also discussed.
文摘The abnormal saturation absorption signal of sodium atom D1 line has been observed in different experimental conditions.The explanation has been presented quantitatively using the velocity-selective optical pumping model.
基金Supported by the National Science Foundation of China。
文摘An optical field induced circular birefringence due to collision-induced Zee-man coherence in Sm with He has been observed.The integrated intensity and linewidth of the signal have been measured as a linear function of buffer gas pressure.The cross section for destruction of orientation in the ground state of Sm with He has been obtained.
基金Supported in part by the Doctoral Programme Foundation of Higli Education Commissionthe National Natural Science Foundation of China.
文摘we present a few unique animal-like fractal patterns in ionized-clnster-beam deposited fullerene-tetracyanoquinodimethane thin films.The fractal patterns consisting of animal-like aggregates such as"fishes"and"quasi-seahorses"have been characterized by transnission electron microscopy.The results indicate that the sall aggregates ofthe aninmal-like body are composed of many single crystals whose crystalline directions are generally different.The formation of tle fractal patterns can be attributed to the cluster-diffusion-lirnited aggregation.
文摘A laser diode pumped cesium beam frequency standard had been built.The laser diode used for both optical pumping and detection is frequency-locked at the 4-4 transition of Cs D2 line.The Voltage controlled crystal oscillator(VCCO)frequency is locked to the center of the Ramsey pattern of the microwave clock transition after frequency multiplying and synthesizing.The preliminary measurement of the frequency stabilities shows that the results are in agreement with the theory,and better results could be achieved by further improving the frequency stability of the laser diode.
基金Supported by the National Natural Science Foundation of Chinathe National Lab.of Machine Perception of Peking University。
文摘A physical-mathematical model was proposed for the NMR relaxation processes,which can automatically identify the multi-relaxation process;the automatic separation of the spin-spin relaxation processes of water sample in a home made phantom was carried out;two kinds of proton pure spin-spin relaxation time images and two kinds of proton computed pure density images have been obtained on a 1.0T supercondlrtive magnet MR-Scanner.
基金Supported by the National Natural Science Foundation of Chinathe 863 Project from Chinese Commission of Science and Technologythe Bundesminusterium fur Forschung und Technologie of Germany.
文摘We report experimental studies on the photorefractive response of KNbO_(3) doubly doped with manganese and rubidium,iron and rubidium,respectively.Two-beam coupling response time in KNbO_(3):Mn:Rb is 3 to 10 times shorter while the two-beam coupling gain coefficient remains almost the same when compare with that in KNbO_(3):Mn.On the other hand,under similar conditions,two-beam coupling response time in KNbO_(3):Fe:Rb is 6 times faster than that in KNbO_(3):Fe.
基金Supported by National Natural Science Foundation of China(No.6881014).
文摘A probe-hole field emission microscope system,controlled by an Apple II computer,has been developed and operated successfully for measuring the work function of a single crystal plane.The work functions on the clean W(100)and W(111)planes are measured to be 4.67eV and 4.45eV,respectively.
基金Project supported by the National Natural Science Foundation of China.
文摘The athermal bioeffects caused by nanosecond electromagnetic pulses with body cells was studied by using a broad band transverse EM-wave cell (BTEM CELL). The experimental system and preliminary mechanism analysis were presented.
基金Project supported by the State Education Commission of Chinathe Grant of Natural Science of Peking University.
文摘Optical and microwave devices with nonlinear materials offer a series of novel phenomena and have many potential applications, so they have received more and more attention. There have been many papers which investigated wave propagation in uniform optical waveguides with nonlinear materials and discovered that they possess the properties of self-focusing and bistability. However, there have rarely been reports on studying the 3-D nonlinear electromagnetic cavities. In the meantime among the methods used to analyze nonlinear optical waveguides, the most commonly used
基金Prdject supported by the National Natural Science Foundation of China and the Climbing Program-National Key Project for Fundamental Research in China.
文摘A concept of frequency character of a chaotic synchronized system (CHSS) is proposed. The nature of the system can be described in the frequency domain with the concept. A simple model to measure the frequency character is designed, and the characteristic curve of Chua’s CHSS is obtained. Some results from theoretical analysis and numerical simulation indicate that the system possesses multiband of frequencies with distinct features shown in each band. Thus it may offer various resources of frequencies, fn particular, it is capable of detecting weak signals drowned in noise in some bands. Both the concept of frequency character and the characteristic curve of CHSS provide a scientific basis for us to gain a deeper insight into the inherent function of information processing in CHSS, and to utilize properly the information resources of CHSS as well.
文摘AI (Artificial Intelligent) control is just the up-to-date frontline of that kind of art, and the most merit it has is that it may provide us with an optimizing control, basing itself merely upon a rough understanding of the plant to be controlled (e. g. an understanding of the type of its inertia, of the limits of variation of those parameters to be controlled, etc.), whenever its exact mathematical model is difficult, even impossible, to build up.
